Itaconic acid, an essential precursor to various products (e.g., acrylic fibers, rubbers, artificial diamonds, and lens), is in high demand in the chemical industry. Conventionally, itaconic acid is isolated from Aspergillus terreus. However, A. terreus grows slowly and does not produce itaconic acid in its spore-forming stage. There is a need for a method that produces itaconic acid in high yield.